Many industrial processes produce a variety of by-products which have significant potential forms as an animal feed or animal feed supplement. For example, the alcoholic brewing industry produces spent yeast as a by-product, this material containing a relatively larger portion of proteinaceous nitrogen and some vitamins, especially vitamin B and consequently the product is used as a protein supplement in animal feeds. Refer, for example, to Applicant's U.S. Pat. No. 4,055,667 and also Canadian Pat. No. 959,332. In addition, the second major by-product of the brewing industry, namely spent brewers' grains, is also utilizable as an animal feed--refer for example to U.S. Pat. No. 3,875,304. A further industry which produces a large volume of by-products also utilizable as animal feeds is the wet corn milling industry, the two major by-products being corn steep water and wet corn bran. The former comprises the condensed corn extractives "steep liquor or water" resulting from the wet milling manufacture of corn starch or syrup which are collected and condensed generally to about 50% solids by evaporation. All of the soluble nutrients in corn grain (for example dissolved vitamins, minerals and other solubles or dispersible nutrients) are contained in the steep water. The corn steep water is handled and stored in tanks and treated in a manner similar to other liquid feed ingredients. The corn steep water is an economical source of protein being equivalent on a dry basis to 44% soybean meal. It is also an excellent source of energy and phosphorus and the dissolved nutrients from the corn which, if not, as is usual, reduced in availability bound to subsequent process steps, would be readily available to the animals. A typical proximate analysis of corn steepwater is as follows:
______________________________________ Crude Protein Fat Fibre Ca P ASH ______________________________________ 50% Dry Matter 22.5% 0 0 0.1% 0.6% 3.9% ______________________________________
and more detailed analyses are readily available in the literature. It may be noted that corn steep liquor per se is quite stable microbiologically and consequently presents no real problems on that account during storage. Wet corn bran comprises that part of the commercial shelled corn remaining after the extraction of the larger portion of starch, gluten and germ by the processes employed in the wet milling manufacture of the corn starch or syrup prior to drying. (It does not, of course, include the extractives i.e. steep water, refer to above.) The product constitutes the corn kernels hull and fibrous particles, and, when utilized alone, may contain an organic acid for extending its shelf life, since the product is extremely prone to microbial degradation. It has a high propensity to heating resulting in significant mold growth within a short period of time, even about twenty-four hours or so, depending on storage conditions. Wet corn bran as exiting the wet corn wet milling process contains 65% moisture and this is usually reduced to about 10% by drying and it can then be used for feed in that condition. A typical analysis of wet corn bran is as follows:
______________________________________ Crude Protein Fat Fibre Ca P Ash ______________________________________ 100% Dry Matter 11.5% 5.0% 10.0% 0.05% 0.20% 2.2% ______________________________________
For a short term feeding of wet corn bran containing an organic acid preservative, a pit silo, a cement slab or a simply constructed wooden box is quite satisfactory to contain the product. Protection from the elements, particularly heavy rains, is highly desirable since the preserving acid may be leached out resulting in the product being subject to spoilage. Wet corn bran is mainly an economic source of energy in ruminant rations but also contributes about 11% protein on a dry matter basis. Both wet corn bran and corn steep liquor have relatively low solid contents, about 35% and 50% respectively, in the state they usually exit the milling process and are not easily or conveniently utilized in that form. In particular, such corn steep liquor when used as an ingredient in traditional liquid feed supplements is subject to re-crystalization and other handling problems. On the other hand bran fibre at the 35% d.m. solids level has a low bulk density and does not compact well with the result that the mass of material is generally air-permeable and/or develops air pockets; the net result in both instances being rapid mold growth. Consequently, in many operations, the wet corn bran, having a moisture content of about 65%, is dried to a moisture content generally below 20% and is then mixed with the corn steep liquor having a moisture content of about 50% and the resulting mixture is dried, in a flash drier or in a steam tube drier, to a moisture content of at most about 10%. This dried product is then sold as an animal feed supplement having a protein content of about 20%. (If corn bran per se is sold as a feed component it too is dried to a moisture content of less then 10% for the same reasons) However, that system has many disadvantages including the following:
1. The expenditure of a large amount of energy in drying the various components and the resulting product.
2. There may be extensive heat denaturation of the nutrients in the resulting product.
3. Valuable heat volatile and/or fine particulate nutrients in the mix being dried are lost by evaporation.
4. The importance of viable Lactobacillus in warm-blooded animals in helping to maintain the proper balance of intestine flora has been documented and, indeed, viable Lactobacillus is sold as a feed supplement for use in appropriate situations. Drying of the product substantially eliminates the Lactobacillus viability thereby removing any possibility of the animals taking advantage of a potential valuable dietary component;
5. There is relatively large capital investment and costly maintenance in the drying equipment required.
6. Operation of the drying equipment results in a pollution problem comprising mainly particulate emissions and very undesirable odour emissions.
7. As in all such wet milling operations, if the drier for the animal feed product becomes inoperative, the whole milling process is been subject to shut-down.
Many ways of utilizing the by-products of the wet corn milling industry, and indeed, the wet wheat milling industry, have been proposed but, to Applicant's best knowledge, all leave a lot to be desired and all generally suffer from one or more of the above disadvantages. A major feature of the prior proposals is that the animal feed product is required to be dried to a relatively low moisture content immediately following its production. Refer for example to U.S. Pat. No. 4,181,748 which discloses a continuous process for refining whole grain corn. This complex process utilizes both a dry milling stage and a wet milling stage, this presumedly, requiring two complete mills since the theoretically possible sequential treatment route would result in a batch operation while the process is stated to be continuous. Moreover, the wet milling stage involves two steeping steps. Various fractions from both the dry milling and wet milling stages are combined to form a wet animal feed composite which, in the usual manner, is dried over a period of hours to form the desired animal feed product. In U.S. Pat. No. 4,171,353, there is disclosed a wet milling process for refining whole grain wheat, in which process again two steeping steps are used and a variety of product streams from the multistage process are combined to form a wet animal feed composite. The composite is then, in the usual manner, dried to a moisture content of from 10-12% by heating at elevated temperatures. A significant claim for this process is that all of the milling is wet milling to avoid damage to the substrate. Other known processes which suffer from similar disadvantages are described in U.S. Pat. Nos. 4,171,383 and 4,171,384. In summary, prior art attempts to use the by-products of wet milling processes have generally required changes to be made to the basic wet milling operation and/or have used a combination of wet and dry milling stages: however, the common feature associated with the various processes is that any wet animal feed composite resulting from such processes are required to be dried immediately, this merely reflecting the widely held industry view that such materials when wet would, invariably, be subject to spoilage within a very short time.
It is an object of the present invention to provide animal feed supplements which, from a practical viewpoint, are in, at most, a moist form, from the wet corn bran and corn steep liquor by-producs of a wet corn milling process, which products are gravitationally and microbiogically stable.
A further object of the present invention is a process for the production of an animal feed supplement from wet corn bran and steep liquor which process is able to utilize those components and especially the wet corn bran in the quantities they are normally produced in any typical wet corn milling plant, the routine operation, and consequently efficiency, of which need not therefore be disrupted.